I would imagine that just because a drug like marijuana is decriminalized folks are not going to run out in droves to start smoking it. Some folks probably buying it off the streets would proably grow it at home for personal consumption. Plus by decriminalizing it you take the profits out of it for the drug cartels and criminal elements and gangs. Which means law enforcement officers would be freed up to do other things. Imagine if the drugs that gangs used to make $$$ were decriminalized and the profit goes way down and puts the dealers out of business. If there is no money in selling drugs because they are legal what do they do?